1. Field of the Invention
This invention relates to a clip-on accessory having a pair of lenses, which may be either filter or powered lenses that are held in registration with a spectacle frame, and which fit directly over the frame. Specifically, the invention resides in the ability of the lens clasp and method of attachment that is utilized in the clip to accommodate a variety of lens thicknesses in a single design. This represents a significant improvement over previous designs.
2. Description of Related Art
Traditionally, a pair of eyeglasses is prescribed with powered lenses to correct optical defects of the human eye. The lenses may be fitted into a variety of frame materials, designs, and shapes. Metal, plastic and rimless frames are the most commonly used in the industry. Due to the high cost of prescription sunglasses, consumers often find it appealing to use clip-on sunglasses in order to protect their eyes from the harmful rays of the sun, and to improve vision in high glare situations and the like. The large variety of frame technologies presents an opportunity for custom-made clip-on sunglasses that can be designed to accommodate a wide range of frame designs and shapes. However, most eyeglass frame designs do not come with a clip-on that is made especially for that specific style of frame. The use on non-prescription, or plano, lenses in clip-on sunglasses allows the wearer to sue the optical properties of the clear lenses that are in their eyeglasses in conjunction with the filtering properties of the clip-on lenses, without influencing the visual acuity derived from the prescription lenses. This arrangement permits a more economical solution to the wearer of prescription eyeglasses, who wants protection from the harmful rays of the sun, or desires to modify the functionality of the prescription eyeglasses by using a powered lens in the clip-on accessory. This arrangement avoids the cost of purchasing a second frame and prescription lenses.
For the purposes of discussion and description, the term filter lens will be used to describe lenses that are used on the clip-on to filter certain wavelengths of light and/or to reduce the amount of visible light. As most frames are not available with a clip designed specifically from the frame, custom made clip-on sunglasses are popular because they allow consumers to choose any frame they prefer, while availing themselves of the cost savings of clip-on.
While clip-on sunglasses are the most common form of clip-on accessory, clip-on may be used for other purposes as well, both functional and cosmetic. For example, a filter lens may be used in a clip-on to increase the contrast that could enhance night vision for driving. Shooting glasses often have a yellow tint and a clip-on could be substituted for a pair of prescription yellow lenses to reduce the cost to the user. Another use of clip-on involves the use of powered lenses in the clip-on to alter the functionality of the prescription lenses they are mounted upon. For example, the use of personal computers has become commonplace, and yet the use of eyewear that is designed for computer use is relatively rare. The distance between a computer screen and the user's eyes can put a strain on the visual system. Computer eyewear can be designed to properly correct the wearer's vision for the distance from the eyes to the screen. Most people over the age of 35 will benefit from such eyewear. The cost of having a separate pair of spectacles may prevent some consumers from availing themselves of having the best possible vision when using a computer. However, a clip-on accessory that supports lenses that change the focal distance of the wearer's primary pair of glasses is a useful and economical alternative.
As the invention permits the use of various thicknesses of lenses, it should be noted that this is a distinct advantage over prior designs that cannot accommodate different thicknesses due to limitations of the clips or the overall design.
It should also be noted that the previous designs of clip-on do not specify the use of specific curvatures of lenses in order to achieve a perfect fit. The use of a single base curve lens in a variety of frame designs permits unwanted light to enter the gaps between the clip-on and the frame. This unwanted light is distracting and can be uncomfortable to the wearer. Our invention specifies the use of lenses that are selected to match the curvature of the frame to provide the finest possible fit, thereby preventing unwanted light from entering the wearer's eyes.